1. Field of the Invention
The invention relates to an optical device, and more particularly to an optical device for camera testing.
2. Description of the Related Art
Referring to FIG. 1, when a test camera 1 is tested in a conventional manner, a test screen 2 is used for image capturing by the a test camera 1, and a distance d between the lens of the test camera 1 and the test screen 2 is adjusted based on definition of the images captured by the test camera 1, so as to determine a back focal length, which leads to an image captured by the test camera 1 to have highest definition with the distance d. However, this method needs a large amount of space to satisfy the required distance d, and operation thereof is inconvenient to conduct.